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[Bug libc/16004] New: memcpy/strcpy: detect memory overlap and crash when error is detected
- From: "slyfox at inbox dot ru" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Sat, 05 Oct 2013 11:29:49 +0000
- Subject: [Bug libc/16004] New: memcpy/strcpy: detect memory overlap and crash when error is detected
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=16004
Bug ID: 16004
Summary: memcpy/strcpy: detect memory overlap and crash when
error is detected
Product: glibc
Version: unspecified
Status: NEW
Severity: enhancement
Priority: P2
Component: libc
Assignee: unassigned at sourceware dot org
Reporter: slyfox at inbox dot ru
CC: drepper.fsp at gmail dot com
Recently amount of bugs regarding to memcpy() copy ordering grown.
I guess it's due to new memcpy@GLIBC_2.14 on new CPUs.
What scary is bugs are always data corruptions and almost never
immediate application crashes (usually seen way later, that in
actual memcpy call). Thus they live very long time unnoticed.
Sometimes bug exhibits only on a subset of hardware (on core i7,
but not core2, same libc) or even oncertain heap. I guess it's
due to different semantics of memcpy IFUNC implelentations
on different host CPUs (depend on linear address alignment).
I'd like to ask to put memory overlap checking right into:
- memcpy implementations themselves before calling assembly implementation
- if above is too heavyweight, then do it only in _FORTIFY_SOURCE mode
- if above is too heavyweight, then add some variable/knob to allow
putting slow checky memcpy at IFUNC startup time.
Same goes for strcpy. Sometimes people do silly things, like
strcpy (some_str, some_str + strlen ("pref"));
and get data corruption.
Thank you!
Some data corruptions I've found myself:
https://bugs.gentoo.org/show_bug.cgi?id=486984 - aircrack-ng's packet parsers
bug with memcpy to move packes for some bytes.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3387206f26e1b48703e810175b98611a4fd8e8ea
- filesystem corruption bug. It's a kernel patch, but usermode linux can be
forced to use libc's memcpy to find such bugs easier.
https://github.com/MidnightCommander/mc/commit/e48cb7c89ff3e54de70130a3de2136a9902a023d
- occasional data corruption of final filepaths
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